The lower the age of schoolchildren, the lower the risk of
school-related uncontrollable infection clusters.
Evidence coming from retrospective and cross-sectional studies early in
the pandemic [28-29] and from larger surveillance studies relating
to the second peak of the pandemic, strongly supports minimal
transmission rates in European day-care centres and primary schools,
both for pupils and educational staff [30-32,42-44]. Significantly,
this finding remains consistent also in areas of high COVID-19
background incidence and after systematic contact testing of each
paediatric index case. Conversely, the only large outbreak of infection
among younger children that has been reported in the literature is most
likely explained by particular epidemiological features and does not
provide conclusive counterevidence [33]. For older children and
adolescents, larger or more numerous clusters of COVID-19 traced back to
school environments have been evidenced, albeit very rarely, pointing to
a potentially non-negligible transmissibility of Sars-CoV-2 in older age
groups that could be explained by social as well as biological factors
[13,34-35].